Real-time compensation method for BDS ephemeris errors based on RINEX 4.0 broadcast earth rotation parameters

Earth rotation parameters (ERP) are crucial for maintaining the Earth reference frame and have significant importance for precise satellite orbit determination. In December 2021, the International GNSS Service (IGS) released the Receiver Independent Exchange (RINEX) version 4.00 protocol, which for the first time included ERP in the broadcast ephemeris. This study utilizes the broadcast ERP from the RINEX 4.00 format to compensate for ephemeris errors. We extract ERP data records from broadcast ephemeris files from 2022 to 2023 to assess the accuracy of GPS and BDS-3 broadcast ERP. An effective data editing method is proposed to address duplicate and anomalous ERP, and the accuracy of GPS and BDS-3 broadcast ERP is evaluated using the IERS C04 product as a reference. The root mean square (RMS) of differences between the GPS broadcast ERP parameters and the C04 product were 2.309 mas for the polar motion parameters and 0.303 ms for the length of day parameter, while the RMS of differences for the BDS-3 broadcast ERP are 2.769 mas, 1.748 mas, and 0.372 ms, respectively. Compared to GPS, the RMS differences for the three BDS-3 parameters increase by 19.9%, 22.0%, and 22.8%, indicating lower accuracy. Based on this, the correlation between broadcast ERP errors and orbital rotation parameters is studied, and a real-time compensation scheme for BDS-3 ephemeris errors using GPS broadcast ERP is designed. Experiments show that this scheme can achieve 40%~60% of the compensation effect of the final IERS C04 product.